1. Field of the Invention
The present invention relates to a video signal processing method, a program for the video signal processing method, a recording medium recording the program for the video signal processing method, and a video signal processing apparatus, which can be applied, for example, to a noise filter for eliminating a nose in a video signal. According to an embodiment of the present invention, a histogram is generated while a characteristic amount which is not suitable to a noise level measurement is excluded and this histogram is analyzed to measure the noise level so that the noise level is measured with a further improved accuracy as compared with a case in related art.
2. Description of the Related Art
In the past, in various video signal processing apparatuses, a method of measuring a noise level of an input video signal and suppressing a noise of the input video signal on the basis of the measurement result, or the like, has been adopted. Regarding this measurement method for the noise level, various techniques by using a histogram have been proposed.
That is, Japanese Unexamined Patent Application Publication No. 8-201464 discloses a method of finding out a plurality of statistical values such as a peak value and an average value from a histogram and setting a small statistical amount as a noise level. Also, Japanese Unexamined Patent Application Publication No. 10-262160 proposes a method of selecting a small value side from among a two-dimensional processing measurement value while an in-plane signal is set as a measurement target and a three-dimensional processing measurement value while a difference signal between fields or between frames is set as a measurement target and finding out a noise level from a peak value of a histogram which uses the measurement value on the selected side. In addition, Japanese Unexamined Patent Application Publication No. 2005-229166 proposes a method of detecting an image area with a high correlativity between adjacent frames and finding out a noise level from a peak value of a histogram which is created from an average value of difference values, a median of the difference values, and the difference values between image areas or the like.
However, according to these disclosed techniques, there is a problem that it is difficult to measure the noise level with a high accuracy because of an influence of a motion difference component included in a signal of the measurement target or a non-flat signal component such as an edge or a texture.